A variety of fibers and fabrics have been made from thermoplastics, such as polypropylene, highly branched low density polyethylene (LDPE) made typically in a high pressure polymerization process, linear heterogeneously branched polyethylene (e.g., linear low density polyethylene made using Ziegler catalysis), blends of polypropylene and linear heterogeneously branched polyethylene, blends of linear heterogeneously branched polyethylene, and ethylene/vinyl alcohol copolymers.
Of the various polymers known to be extrudable into fiber, highly branched LDPE has not been successfully melt spun into fine denier fiber. Linear heterogeneously branched polyethylene has been made into monofilament, as described in U.S. Pat. No. 4,076,698 (Anderson et al.), the disclosure of which is incorporated herein by reference, and into fine denier fiber, as disclosed in U.S. Pat. No. 4,644,045 (Fowells), U.S. Pat. No. 4,830,907 (Sawyer et al.), U.S. Pat. No. 4,909,975 (Sawyer et al.) and in U.S. Pat. No. 4,578,414 (Sawyer et al.), the disclosures of which are incorporated herein by reference.
Blends of such heterogeneously branched polyethylene have also been successfully made into fine denier fiber and fabrics, as disclosed in U.S. Pat. No. 4,842,922 Krupp et al.), U.S. Pat. No. 4,990,204 (Krupp et al.) and U.S. Pat. No. 5,112,686 (Krupp et al.), the disclosures of which are all incorporated herein by reference.
In addition to heterogeneously branched LLDPE, fibers have also been made from narrow molecular weight distribution ethylene copolymers produced using the so called single site catalysts as described by Davey et al., in U.S. Pat. No. 5,322,728 and WO 94/12699.
Fibers have also been made from other polymeric materials. U.S. Pat. No. 4,425,393 (Benedyk) discloses monofilament fiber made from polymeric material having an elastic modulus from 2,000 to 10,000 psi. which includes plasticized polyvinyl chloride (PVC), low density polyethylene (LDPE), thermoplastic rubber, ethylene-ethyl acrylate, ethylene-butylene copolymer, polybutylene and copolymers thereof, ethylene-propylene copolymers, chlorinated polypropylene, chlorinated polybutylene or mixtures of those.
Many applications for such fibers require varying degrees of softness or stiffness and have different operating temperature requirements depending upon the application. For instance U.S. Pat. No. 5,068,141 (Kubo et al.) discloses making nonwoven fabrics from continuous heat bonded filaments of certain heterogeneously branched LLDPE having specified heats of fusion.
The present invention relates to fibers and fabricated articles therefrom prepared from polymer compositions which comprise at least one substantially random interpolymer comprising polymer units derived from one or more .alpha.-olefin monomers with one or more vinyl or vinylidene aromatic monomers and/or a hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers or blends therefrom. Unique to these novel materials is the ability to precisely tune both the glass transition process (location, amplitude and width of transition) in the vicinity of the ambient temperature range, and the stiffness and modulus of the material in its final state. Both these factors can be controlled by varying the relative amount of .alpha.-olefin(s) and vinyl or vinylidene aromatic and/or hindered aliphatic vinyl or vinylidene monomers in the final interpolymer or blend therefrom. Further variation in the Tg of the polymer composition used in the present invention can be introduced by variation of the type of component blended with the substantially random interpolymer including the presence of one or more tackifiers in the final formulation. This control of the Tg and modulus allows the stiffness or softness of the fiber to be varied to suit a given application.